Double $J/\psi$ production in pion-nucleon scattering at COMPASS

TL;DR

This study measures double $J/\psi$ production in pion-nucleon scattering at COMPASS, finding single parton scattering dominates and setting limits on intrinsic charm, with no evidence for exotic tetraquarks.

Contribution

First measurement of double $J/\psi$ production in pion-nucleon scattering at COMPASS, analyzing production mechanisms and constraining intrinsic charm and exotic states.

Findings

Single parton scattering explains the data.

Upper limit set on pion's intrinsic charm content.

No evidence found for exotic tetraquark states.

Abstract

We present the study of the production of double $J/\psi$ mesons using COMPASS data collected with a 190 GeV/$c$ $\pi^-$ beam scattering off NH$_{3}$, Al and W targets. Kinematic distributions of the collected double $J/\psi$ events are analysed, and the double $J/\psi$ production cross section is estimated for each of the COMPASS targets. The results are compared to predictions from single- and double-parton scattering models as well as the pion intrinsic charm and the tetraquark exotic resonance hypotheses. It is demonstrated that the single parton scattering production mechanism gives the dominant contribution that is sufficient to describe the data. An upper limit on the double intrinsic charm content of pion is evaluated. No significant signatures that could be associated with exotic tetraquarks are found in the double $J/\psi$ mass spectrum.